1. Field of the Invention
The present invention relates to a chip mounting apparatus for picking up each of a large number of chips, for example, semiconductor chips, chip capacitors, chip resistors or the like bonded on an adhesive expand tape to mount it onto a package or a printed board.
2. Description of the Prior Art
In general, a large number of semiconductor elements are initially formed into a certain pattern on a semiconductor wafer and are then individually separated into generally square chips through dicing, through dicing and breaking or through scribing and breaking. Prior to subsequent die-bonding and sorting process, the separated semiconductor chips are successively transported to a chip mounting apparatus, while being bonded on an adhesive expand tape, so as to be picked up thereby one at a time. The chip mounting apparatus is provided with a vacuum pickup collet for picking up the chips one by one and a push rod or rods for pushing up each chip towards the collet. In this apparatus, the adhesive expand tape is separated from each chip by drawing the tape downwards in a state in which the chip is attracted by the collet and kept unmoved by the push rods.
Recently, each semiconductor chip tends to be formed into a large size, rendering its bonding area to be enlarged. This fact makes it more difficult to separate the tape from the chip. Because of this, the period of time required for pushing up the chip by the push rods has sometimes been prolonged. However, even if the semiconductor chips are the same in external size, the time required for separating each chip from the tape is not fixed. For example, when the semiconductor chips are each 10 mm square, the time required for the separation varies in the range of 0.5 to 15 seconds. To make the separation time constant, the longest one is required to be set as the basic period thereof. As a result, even when a certain chip is separated from the tape within a relatively short time, it is picked up by the collet upon lapse of the basic period of separation time. This is disadvantageous in that productivity is relatively low.